Joint immobilization after anterior cruciate ligament (ACL) reconstruction may lead to intra-articular adhesions and range of motion deficits. Some practitioners thus advocate for the use of postoperative continuous passive motion (CPM) machine protocols. However, previous studies have failed to show CPM to be effective in increasing postoperative range of motion. Continuous passive motion has, however, been shown to reduce rates of arthrofibrosis requiring manipulation under anesthesia (MUA) in adult populations. To date, there has been no study of the efficacy of CPM after ACL reconstruction in a pediatric population. This was a retrospective cohort study of pediatric patients (age <20 years) who underwent primary ACL reconstruction at an urban tertiary care children's hospital. Clinically significant arthrofibrosis was defined as reduced knee flexion requiring MUA within 6 months of surgery. The final dataset included 163 patients. There was no significant difference between cohorts in range of motion at the 1-week, 1-month, 3-month, and 6-month time points (P=.137, .695, .897, and .339, respectively). The 2 cohorts also did not differ significantly in pain scores at these time points (P=.684, .623, .507, and 1.000, respectively). At 3 and 6 months, neither quadriceps nor hamstrings strength differed significantly between cohorts. Four patients (7.4%) in the no-CPM cohort required MUA for arthrofibrosis within 6 months of surgery, while no patients in the CPM cohort required MUA (P=.023). This suggests that CPM use reduces arthrofibrosis requiring MUA in pediatric patients after ACL reconstruction. Future work may better define the clinical utility and cost-effectiveness of CPM in rehabilitation after these surgeries. [Orthopedics. 2019; 42(1):e81–e85.]